[libvirt] [PATCH v1 01/18] add macros for implementing automatic cleanup functionality

[Erik Skultety]

On Sun, Jun 03, 2018 at 01:41:59PM +0530, Sukrit Bhatnagar wrote:
> New macros are added to src/util/viralloc.h which help in
> adding cleanup attribute to variable declarations.
>
> Signed-off-by: Sukrit Bhatnagar <skrtbhtngr at gmail.com>

If you recall the recent RFC thread [1], I agreed with Pavel that we should
introduce complete changes to each file, so that we don't need to track was has
been already done for what file and what is still missing, so the series would
look something like this:

1) vir<some_file>.c preparations (especially VIR_{AUTOPTR,AUTOCLEAR} might need
that)
2) Use VIR_AUTOFREE across vir<some_file>.c
3) Use VIR_AUTOPTR across vir<some_file>.c
4) Use VIR_AUTOCLEAR across vir<some_file>.c

...One more thing, the commit subject of every patch in the current series
should probably look like this:
util: <module>: Use VIR_AUTOFREE instead of VIR_FREE for scalar types

and the corresponding commit message:
By making use of the GCC's __attribute__((cleanup)) handled by VIR_AUTOFREE
macro, majority of the VIR_FREE calls can be dropped, which in turn leads to
getting rid of most of our cleanup sections.

[1] https://www.redhat.com/archives/libvir-list/2018-May/msg02391.html

Erik

> ---
>  src/util/viralloc.h | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 69 insertions(+)
>
> diff --git a/src/util/viralloc.h b/src/util/viralloc.h
> index 69d0f90..bb37c48 100644
> --- a/src/util/viralloc.h
> +++ b/src/util/viralloc.h
> @@ -596,4 +596,73 @@ void virAllocTestInit(void);
>  int virAllocTestCount(void);
>  void virAllocTestOOM(int n, int m);
>  void virAllocTestHook(void (*func)(int, void*), void *data);
> +
> +# define VIR_AUTOPTR_FUNC_NAME(type) virAutoPtr##type
> +# define VIR_AUTOCLEAR_FUNC_NAME(type) virAutoClear##type
> +
> +/**
> + * VIR_DEFINE_AUTOPTR_FUNC:
> + * @type: type of the variables(s) to free automatically
> + * @func: cleanup function to be automatically called
> + *
> + * This macro defines a function for automatic freeing of
> + * resources allocated to a variable of type @type. The newly
> + * defined function calls the corresponding pre-defined
> + * function @func.
> + */
> +# define VIR_DEFINE_AUTOPTR_FUNC(type, func) \
> +    static inline void VIR_AUTOPTR_FUNC_NAME(type)(type *_ptr) \
> +    { \
> +        (func)(*_ptr); \
> +    } \
> +
> +/**
> + * VIR_DEFINE_AUTOCLEAR_FUNC:
> + * @type: type of the variables(s) to free automatically
> + * @func: cleanup function to be automatically called
> + *
> + * This macro defines a function for automatic clearing of
> + * a variable of type @type. The newly deifined function calls
> + * the corresponding pre-defined function @func.
> + */
> +# define VIR_DEFINE_AUTOCLEAR_FUNC(type, func) \
> +    static inline void VIR_AUTOCLEAR_FUNC_NAME(type)(type *_ptr) \
> +    { \
> +        (func)(_ptr); \
> +    } \
> +
> +/**
> + * VIR_AUTOFREE:
> + * @type: type of the variables(s) to free automatically
> + *
> + * Macro to automatically free the memory allocated to
> + * the variable(s) declared with it by calling virFree
> + * when the variable goes out of scope.
> + */
> +# define VIR_AUTOFREE(type) __attribute__((cleanup(virFree))) type
> +
> +/**
> + * VIR_AUTOPTR:
> + * @type: type of the variables(s) to free automatically
> + *
> + * Macro to automatically free the memory allocated to
> + * the variable(s) declared with it by calling the function
> + * defined by VIR_DEFINE_AUTOPTR_FUNC when the variable
> + * goes out of scope.
> + */
> +# define VIR_AUTOPTR(type) \
> +    __attribute__((cleanup(VIR_AUTOPTR_FUNC_NAME(type)))) type
> +
> +/**
> + * VIR_AUTOCLEAR:
> + * @type: type of the variables(s) to free automatically
> + *
> + * Macro to automatically clear the variable(s) declared
> + * with it by calling the function defined by
> + * VIR_DEFINE_AUTOCLEAR_FUNC when the variable goes out
> + * of scope.
> + */
> +# define VIR_AUTOCLEAR(type) \
> +    __attribute__((cleanup(VIR_AUTOCLEAR_FUNC_NAME(type)))) type
> +
>  #endif /* __VIR_MEMORY_H_ */
> --
> 1.8.3.1
>
> --
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